I was employeed with a company from 1993-2000 and again from 2000-2003. Both times I participated in the 401K program, and left my money in the program. I recently received a statement indicating that I was only 60% vested. Shouldn't I be 100% vested since I have over 5 yrs total work tenure with the company?

Depends on the company rules for a break in service. Most companies have rules that govern whether a break in service will restart the vesting clock or not. Check with your Benefits Admin on that issue.

Scott is correct, when you left the first time, the money you had was not vested and most companies I have worked for require continuious service for vesting. But it will be up to the rules of the exact plan.